The present invention relates to a Veress-type pneumoneedle and, more particularly, is directed to such a needle which may be of the single use disposable type. In its more specific aspects, the invention is concerned with a pneumoneedle in which the stylet of the needle forms part of an assembly which may be removed to open the needle.
Veress-type pneumoneedles have a spring-loaded stylet which is slidably received within a hollow needle. In use for abdominal endoscopy, once the pneumoneedle penetrates the abdominal wall and enters the cavity, resistance against the end of the needle ceases and a spring pushes the blunt end of the stylet beyond the sharp tip of the needle.
The pneumoneedles introduced by Veress in the late 1930s were reusable. The stylets in such needles carry a valve assembly which is pushed rearward by the resistance on the needle end and is biased forwardly by a spring when the resistance is removed. With this design, the body of the needle must be grasped forwardly of the valve assembly to avoid imparting force to the stylet.
U.S. Pat. No. 4,808,168 discloses a disposable pneumoneedle wherein the valve assembly is fixed to a housing which slidably carries the stylet. A spring within the housing biases the stylet forwardly through the needle and permits the stylet to retract upon encountering resistance. Because the valve assembly is carried by the housing, rather than the stylet, force applied to the assembly does not interfere with such retraction of the stylet.
In the pneumoneedle of U.S. Pat. No. 4,808,168, the needle, housing, stylet, spring and valve form an assembly which cannot be taken apart, without destruction. As a result, the stylet is always disposed within the needle and cannot be removed to permit access through the needle.